Criminal Network Analysis, which is a broad category of terrorist network analysis, can be categorized into three generations (Xu J., Chen H., 2006):

First generation: Manual approach. The representation of first generation is known as Anacapa chart (Klerks, 2001). Using this approach, an analyst should first develop an association matrix by detecting criminal associations from raw data. Then, a link chart for visualization purposes can then be drawn based on the association matrix. For example, to map the terrorist network containing the 19 hijackers in 9/11 attacks, Krebs (Krebs, 2002) gathered data about the relationships among the hijackers from publicly available information reported in several major newspapers. Krebs then manually constructed an association matrix to incorporate these relations (Krebs, 2002) and illustrated a network representation in order to analyze the structural properties of the network.

It is well known fact that such a manual approach for criminal network analysis is helpful in crime investigation; but this type of approach is would be good if the dataset is short, but it would be difficult rather impossible to draw a link chart if there are thousands of nodes.

Second generation: Graphic-based approach. These tools can automatically produce graphical representations of criminal networks. Most of the available network analysis tools belong to this generation. Among them Analyst’s Notebook, Netmap and XANALYS Link Explorer (previously called Watson) are the most popular (Xu, J., Chen H., 2006). It is to mention that, Analyst’s Notebook (see Figure 2.3) can automatically generate a link chart [based on relational data from a spread sheet or text file.]

First generation: Manual approach. Representative of the first generation is the Anacapa Chart [EN 6]. With this approach, an analyst must first construct an
association matrix by identifying criminal associations from raw data. A link chart for visualization purposes can then be drawn based on the association matrix. For example, to map the terrorist network containing the 19 hijackers in the September 11 attacks, Krebs [EN 8] gathered data about the relationships among the hijackers from publicly released information reported in several major newspapers. He then manually constructed an association matrix to integrate these relations [EN 8] and drew a network representation to analyze the structural properties of the network (Figure 1).

Although such a manual approach for criminal network analysis is helpful in crime investigation, it becomes an extremely ineffective and inefficient method when data sets are very large.

Second generation: Graphic-based approach. These tools can automatically produce graphical representations of criminal networks. Most existing network analysis tools belong to this generation. Among them Analyst’s Notebook [EN 7], Netmap [EN 5], and XANALYS Link Explorer (previously called Watson) [EN 1], are the most popular. For example, Analyst’s Notebook can automatically generate a link chart based on relational data from a spreadsheet or text file (Figure 2a).